1. Field of the Invention
The present invention relates to a magnetic recording and reproducing apparatus for recording and reproducing plural types of data signals of different data rate.
2. Description of the Related Art
As a magnetic recording and reproducing apparatus for recording and reproducing, for example, video signals as data signals on a magnetic tape (VTR), a digital VTR for recording and reproducing digitized data of video signals is known. FIG. 1 shows a conventional block diagram of such digital VTR, in which numeral 50 denotes an input terminal for digital data relating to, video signals, for example, numeral 31 denotes a record process unit, 32 denotes a digital modulator, 53, 54 denote heads mutually different in the azimuth, disposed to confront each other at 180 degrees on a rotary drum 57, 58 denotes a magnetic tape, 60 denotes a digital data output terminal, 41 denotes a reproduction process unit, and 42 denotes a digital demodulator.
Digital data such as video signals inputted to the digital data input, terminal 50 at the time of recording are fed in the record process unit, 31. The record process unit 31 codes the digital data for error correction to detect and correct an error, and outputs the coded digital data to the modulator 32. In the modulator 32, the inputted digital codes are transformed into signals in a form suited to recording, and are output to be recorded on the magnetic tape 58 by the magnetic heads 53, 54 on the rotary drum 57.
The signal reproduced by the magnetic heads 53, 54 at the time of reproduction is transformed into the original digital code in the demodulator 42. The reproduction process unit 41 decodes for error correction, detecting and correcting the error caused in the process of recording and reproduction. reproduction process unit 41, The digital data in the same signal form as in recording is outputted from the digital data output terminal 60.
Incidentally, when recording video signals, such a digital VTR, it is desired as to record different signal forms, that is, different in data quantity, of the HDTV being put in practical use and the existing television signals by NTSC system in the same apparatus. Moreover, in such a digital VTR, it is also desired to record digital codes of the same signal form but different in data quantities corresponding to the length of recording time by the same apparatus. In other words, the VTR must record and reproduce data of different data rates in the same apparatus.
However, in the composition of the conventional digital VTR shown in FIG. 1, recording and reproducing data can only be performed at the same data rate.